YAZOO CITY, Miss. – A slow migration unfolded in central Mississippi on Thursday, with people and animals seeking higher ground to escape the flooding from the Mississippi River and its tributaries.

In Louisiana, water poured over a century-old levee, flooding 12,000 acres of corn and soybeans despite farmers’ frantic efforts to shore up the structure. Downstream, officials with the Port of New Orleans said the Coast Guard could close the river to ships as early as Monday, halting traffic on one of the world’s busiest commercial waterways.

After swamping low-lying neighborhoods in Memphis, Tenn., earlier this week, the rising water is bringing misery to farms and small waterfront communities in Mississippi, Louisiana and Arkansas.

The Army Corps of Engineers is considering whether to open the Morganza spillway, which would flood thousands of homes and acres of farmland along a 100-mile stretch in Louisiana but take the pressure off levees and help to protect Baton Rouge, New Orleans and the oil refineries in between. A decision is expected in the next several days.

In Yazoo City, Miss., Brett Robinson drove slowly down River Road near his farm Thursday, staring at corn fields that are beginning to look like lakes.

In Bunche’s Bend, in the northeastern corner of Louisiana, there was heartbreak in the voice of farmer Ted Schneider, 50, as he watched the muddy river creep into his 2,800 acres of soybeans.

“It’s kind of discouraging to look out here and think about all that work and money and know it is all going to be gone in a few days,” said Schneider, who has farmed the land since 1984.

Maintenance on the levee was abandoned years ago after a higher levee was built farther back, leaving a sliver of farmland in between vulnerable. Officials are confident that levee will hold, but that’s small comfort to the farmers whose land is flooding.

About 40 of them worked in recent days to stack 1,800 sandbags along the older levee’s weakest points, but their efforts were no match for the river, which crested higher than originally forecast.

Farther south, other communities were keeping a close watch on their levees and taking action to shore up potential trouble spots. Sandbags were being placed along a portion of New Orleans’ French Quarter riverfront, although the city isn’t expecting a major impact from the flood.

Chris Bonura, a spokesman for the Port of New Orleans, said the Coast Guard plans to close a 190-mile stretch of river from Baton Rouge to the Gulf of Mexico when the water reaches the 18-foot level at a gauge in Carrollton, which could happen by Monday.

The mouth of the Mississippi would become crowded with ships with nowhere else to go, although some might be diverted to other ports.

Barges headed south from the nation’s heartland to the Port of South Louisiana at Reserve, upriver from New Orleans, would be unable to reach grain elevators.

Massive ships that carry U.S. corn, soybeans and other crops out of the country would be unable to move. Shipments of Venezuelan heavy crude oil that come in by tanker to a refinery in Chalmette would be locked out of the river, although most refineries on the river are fed by pipelines.

In the poverty-stricken Mississippi Delta, meanwhile, people waited uneasily to see how high the water would get. About 600 homes in the Delta have flooded in the past several days as the water has risen toward some of the highest levels on record.

Residents watch the flood creep closer every day to their crops and homes and there’s little they can do but wonder how bad it will be.

“Waiting is the hardest part,” said Ed Jordan, whose family has farmed in the Carter community for four generations. “Everybody around here is going to catch the blues. This is the true Mississippi blues.”

Swollen by weeks of heavy rain and snowmelt, the Mississippi River has been breaking high-water records that have stood since the 1920s and ’30s. It is projected to crest at Vicksburg on May 19 and shatter the mark set there during the cataclysmic Great Flood of 1927. The crest is expected to reach New Orleans on May 23.